Bài làm

Bài 1 : Tính nhanh 

a) 10000 - 47x 7 -47 x 28

= 47x(10000-28)

=47x9972

=468684

b) 54x 47 - 53x 47 - 47

=47x(54-53)-47

=47x1-47

=47-47

=0

c)175 x 1274 - 175 x 273 - 175

=175x(1274-273)-175

=175x1001-175

=175175-175

=175000

# Chúc bạn học tốt #

kho nhi

1000 - 47 . 72 - 47 .28

= 47 . ( 1000 - 72 -28 )

= 47 .0

=0

3457 - 27 . 48 - 48 .73 + 6543

=3457 - 48 . (27 + 73 ) + 6543

= 3457 - 4800 + 6543

= 5200

a) \(\left(145\times99+145\right)-\left(143\times102-143\right)\)

\(=\left[145\times\left(99+1\right)\right]-\left[143\times\left(102-1\right)\right]\)

\(=\left(145\times100\right)-\left(143\times101\right)\)

\(=14500-14443\)

\(=57\)

b) \(54\times47-47\times53-20-27\)

\(=47\times\left(54-53\right)-20-27\)

\(=47-20-27\)

\(=0\)

c) \(10000-47\times72-47\times28\)

\(=10000-47\times\left(72+28\right)\)

\(=10000-47\times100\)

\(=10000-4700\)

\(=5300\)

d) \(3457-27\times48-48\times73+6543\)

\(=\left(3457+6543\right)-48\times\left(27+73\right)\)

\(=10000-48\times100\)

\(=10000-4800\)

\(=5200\)

\(2b,\)\(54\times47-47\times53-20-27.\)

\(=47\times54-47\times53-47\)

\(=47\times\left(54-53-1\right)\)

\(=47\times0=0\)

\(2c,\)\(10000-47\times72-47\times28\)

\(=100\times100-47\times\left(72+28\right)\)

\(=100\times100-47\times100\)

\(=100\times\left(100-47\right)\)

\(=100\times53=5300\)

2b

54 x 47 - 47 x 53 - 20 - 27 = 47 x ( 54 - 53 ) - 20 - 27 = 47 - 20 - 27 = 47 - ( 20 + 27 ) = 47 - 47 = 0

2c

10000 - 47 x 72 - 47 x 28 = 10000 - 47 x ( 72 - 28 ) = 10000 - 47 x 44 = 10000 - 2068 = 7932

10000 - 47 × 72 - 47 × 28

= 100 × 100 - 47 × (72 + 28)

= 100 × 100 - 47 × 100

= 100 × (100 - 47)

= 100 × 53 = 5300

` 10000 – 47 xx 72 – 47 xx 28 `
`=10000-47xx(72+28)`
`=10000-47xx100`
`=100xx100-47xx100`
`=100xx(100-47)`
`=100xx53`
`=5300`

`10 000 - 47 xx 72 - 47xx28`

`=10 000 - 47 xx(72+28)`

`=10 000 - 47xx100`

`=10 000 - 4700`

`=5300`

 10000 – 47 x 72 + 47 x 28 

=10000-(47x(72+28)

=10000-4700

=5300

\(\begin{array}{*{20}{c}}{ + \begin{array}{*{20}{c}}{47}\\{43}\end{array}}\\\hline{\,\,\,90}\end{array}\)                                     \(\begin{array}{*{20}{c}}{ + \begin{array}{*{20}{c}}{43}\\{47}\end{array}}\\\hline{\,\,\,90}\end{array}\)

\(\begin{array}{*{20}{c}}{ + \begin{array}{*{20}{c}}{65}\\{28}\end{array}}\\\hline{\,\,\,\,93}\end{array}\)                                     \(\begin{array}{*{20}{c}}{ + \begin{array}{*{20}{c}}{28}\\{65}\end{array}}\\\hline{\,\,\,93}\end{array}\)

đáp án lần lượt:90,90,93,93

dễ tự là

c)(145x99+145)-(143x102-143)

   =   145x(99+1)-143x(101-1)

    =  145x100-143x100

      =     (145-143)x100

       =           2x100

          =          200